Where is io.sockets.adapter.rooms in io of nodejs?

https://stackoverflow.com/a/6727354/462608

The short answer:
io.sockets.adapter.rooms

I analysed io:

The sockets output part from io as shown in that answer contains the following:

sockets: 
   { manager: [Circular],
     name: '',
     sockets: { '210837319844898486': [Object] },
     auth: false,
     flags: { endpoint: '', exceptions: [] },
     _events: { connection: [Function] } },

Where is the adapter? Where are the rooms?

What is the way to find out adapter and rooms from the output of io?

Answer

I think you are trying to get room before joining it. First You have to Join room and than you can get the rooms in io.sockets.adapter.rooms You can checkout this link to know rooms

let room_id = 111

io.sockets.on("connection", function (socket) {
    // Everytime a client logs in, display a connected message
    console.log("Server-Client Connected!");
    socket.join("_room" + room_id);
    socket.on('connected', function (data) {

    });
    console.log(io.sockets.adapter.rooms);
    socket.on('qr_code_scan', function (room_id) {
        io.sockets.in("_room" + room_id).emit("qr_code_scan", true);
    });
});

Log of io.sockets.adapter.rooms

{bjYiUV5YZy54VedKAAAA: Room, _room111: Room}
app.js:55
_room111:Room {sockets: {…}, length: 1}
length:1
sockets:{-isBAZIB-Sm3jArgAAAB: true}
-isBAZIB-Sm3jArgAAAB:true
__proto__:Object
__proto__:Object
-isBAZIB-Sm3jArgAAAB:Room {sockets: {…}, length: 1}
length:1
sockets:{-isBAZIB-Sm3jArgAAAB: true}
-isBAZIB-Sm3jArgAAAB:true
__proto__:Object
__proto__:Object
__proto__:Object